Concrete Mix Proportion Research Articles

Structural performance of steel fibre reinforced concrete — Part IV. Toughness properties

The present paper of a series deals with the experimental characterisation of flexural toughness properties of structural concrete containing different volume of hooked-end steel fibre reinforcement (75 kg/m3, 150 kg/m3). Third-point flexural tests were carried out on steel fibre reinforced concrete beams having a cross-section of 80 mm × 85 mm with the span of 765 mm, hence the shear span to depth ratio was 3. Beams were sawn out of steel fibre reinforced slab elements (see Part I) in order to take into consideration the introduced privilege fibre orientation (I and II) and the position of the beam (Ba-a, Ba-b, Ba-c) before sawing (see Part I). Flexural toughness properties were determined considering different standard specifications, namely the method of the ASTM (American Standards for Testing Materials), the process of the JSCE (Japan Society of Civil Engineering), and the final proposal of Banthia and Trottier for the post cracking strength. Consequently, behaviour of steel fibre reinforced concrete was examined in bending taking into consideration different experimental parameters such as fibre content, concrete mix proportions, fibre orientation, positions of test specimens in the formwork, while experimental constants were the size of specimens, the type of fibre used and the test set-up and test arrangement.

The Effect of Polyvinyl Alcohol (PVA) on the Mix Proportion of Oil Palm Shell (OPS) Concrete

Oil palm shell (OPS) is a renewable resource obtained from agricultural solid waste after the extraction of palm oil. It has been previously reported that OPS can be used as a coarse aggregate substitute in the manufacture of structural lightweight concrete. Since OPS is an organic material, its properties may degrade after a certain period of time unless pre-treatment is applied on the aggregates. Polyvinyl alcohol (PVA) can be used to treat the OPS before being incorporated as coarse aggregates in concrete. It has been determined that the use of PVA as pre-treatment enables an improvement to the properties of raw OPS aggregates and consequently the resulting concrete. In this research work, the effect of PVA as pre-treatment on OPS aggregates on the mix proportion of OPS concrete was investigated. The results show that there was an increase in the slump values of the OPS concrete made with PVA treated OPS aggregates. The 28-day air-dry density and compressive strength of PVA treated OPS concrete slightly increased as compared to raw OPS concrete.

Mix Proportion of Concrete Containing Oil Palm Wastes as Replacement for Conventional Constituents

Oil palm waste materials which consist of palm oil fuel ash (POFA) and oil palm shell (OPS) are contributing negatively towards the environment as they are normally disposed in landfills. In recent years, research studies found that POFA and OPS can be used as potential replacements for cement and coarse aggregates respectively in the effort to solve the environmental problems contributed by these wastes. In this study, POFA was used to replace ordinary Portland cement at 15% by weight of binder while OPS fully replaced the coarse aggregates to produce lightweight concrete. A suitable mix proportion for OPS concrete was determined through several trial mixes and then cement was partially replaced by POFA to produce POFA OPS concrete. The POFA OPS concrete registered density of 1870 kg/m3 which categorises it as a lightweight concrete. This concrete also produced slump value of 100 mm and compressive strength of 25.50 and 30.50 MPa at age 7 and 28 days respectively.

A modified method for the design of pervious concrete mix

As a new material type for pavement, pervious concrete should be designed to maintain both porosity and the structural strength. The actual mix proportions for pervious concrete depend on the application, the mechanical properties required and the materials used. Actually, the mix proportions of pervious concrete were determined for locally available materials based frequently on trial batching and experience. Another analytical method should be developed to facilitate the concrete producers. Based on the assumption that the cement paste only plays a role of coating, it does not fulfill the void among the grains of gravel; this paper focuses on one modified method for the design of the pervious concrete. The volume cement paste is divided by the surface area of the aggregates to determine the thickness of the excess paste. A scaling factor has been defined to evenly distribute the cement paste toward the size of gravel. Moreover, a binder drainage test is proposed to determine the critical w/c ratio towards to prevent the flow of cement paste to the lower layers of concrete under the action of vibration or compaction. The pervious concrete has been formulated according to this method to validate it. The mechanical and hydraulic tests are performed to characterize the pervious concrete. The obtained pervious concrete presents a large sufficient permeability (1mms−1) for draining rainwater and good mechanical resistance (Rc=28.6MPa) with regard to typical pervious concrete applications such as parking lots, walkways and low-traffic roadways. In addition, the mechanical strength of pervious concrete in this research is found higher than that generally reported by other authors. The results indicate that the theoretical mix design method is a successful theory for an optimizing composition of pervious concrete.

Assessing particle packing based self-consolidating concrete mix design method

A particle-packing based mix design method, originally proposed by Brouwers, is modified and applied to the design of self-consolidating concrete (SCC) mix proportions. The essence of this method is to improve particle packing of the concrete system and reduce the paste quantity while maintaining concrete quality and performance. Using this method, a large matrix of SCC mixes, made of different aggregate types, sizes, and supplementary cementitious material (SCMs) types, was designed to have a particle distribution modulus (q) ranging from 0.23 to 0.29. Fresh properties (such as flowability, passing ability, segregation resistance, yield stress, viscosity, set time and formwork pressure) and hardened properties (such as compressive strength, surface resistance, shrinkage, and air structure) of these concrete mixes were experimentally evaluated. The concrete mixes designed using the modified Brouwers mix design algorithm and particle packing concept had a potential to reduce up to 20% binder content compared to existing SCC mix proportioning methods and still maintain good performance.

Effects of Old Aggregate on Concrete Strength

The basic characteristics of recycled coarse aggregate are completely tested. Crushed the waste concrete through artificial crushing, configured recycled concrete by reference to the mix proportion of ordinary concrete . Through experiments, recycled concrete and ordinary concrete basic properties were tested, the performance of recycled concrete with different coarse aggregate were compared, calculated the strength and amount of mold of recycled concrete; results showed that the basic properties of recycled coarse aggregate and natural aggregate existed certain differences. compared to the pebble-based recycled aggregate concrete strength can reach ordinary concrete strength, and when the new coarse aggregate and recycled coarse aggregate were the half, the strength of concrete was not high, the stress - strain curve and the ordinary concrete stress - strain curves were similar, destructive phenomenons of test cubes were close with ordinary concrete .

대형 터빈 기초 구조물의 온도균열 제어에 관한 연구

최근 증가 추세에 있는 화력발전소 건설에 있어서, 터빈 기초 구조물은 규모가 매우 큰 매스콘크리트이다. 매스콘크리트의 수화열은 구조물의 품질과 공기 등에 중대한 영향을 미치는 요인 중 하나이므로, 수화열 제어를 위한 적절한 방안은 필수적이다. 이 연구에서는 국내 복합화력발전소 터빈 기초 시공에 앞서 수화열 해석을 통하여 수화열 균열 발생 가능성을 예측하고, 수화열 제어 방안으로서 콘크리트 배합 및 양생방법 변경을 제안하였다. 콘크리트 배합은 기존 1종 보통시멘트 콘크리트 배합에서 슬래그시멘트 콘크리트 배합으로 변경을 제안하였고, 기존 양생포 및 살수양생방법을 개선하기 위하여 매스콘크리트 중심부와 표면부의 온도를 모니터링하여 온도차를 일정수준 이하로 일정하게 유지시켜주는 양생자동화시스템을 적용한 양생방법을 제안하였다. 실제 시공시에는 슬래그콘크리트 배합을 사용하고, 2기의 동일한 터빈 기초 구조물에 대하여 각각 보온양생공법과 양생자동화시스템을 적용하여 양생방법에 따른 온도균열 제어효과를 비교하였으며, 2기의 매스콘크리트에서 온도, 변형률 모니터링 및 균열 조사를 통하여 수화열 제어 효과를 평가하였다.

Durability properties of a concrete with waste glass sludge exposed to freeze-and-thaw condition and de-icing salt

Waste glass sludge (WGS), a byproduct of glass plate manufacture, was used to improve the durability properties of concrete under an environmental condition of freezing and thawing, with the existence of de-icing salts. A total of five concrete mix proportions were prepared, by varying the amounts of WGS. In order to observe the effects and roles of WGS on the durability performances of concrete mixtures, compressive strength tests, freezing and thawing tests, chloride ion penetration and surface scaling were carried out. Test results showed that the incorporation of WGS as a partial replacement for cement has beneficial effects on the compressive strength of concrete, especially when used together with fly ash. Moreover, WGS improved the resistance of freezing and thawing with and without de-icing salts, the chloride ion penetration and the resistance of surface scaling of the concrete compared to the control mixture containing 20% fly ash as cement replacement.

Numerical analysis of drying shrinkage in long reinforced concrete structure

Drying shrinkage is one of the most important inducements to concrete cracking in long structures. To investigate the phenomenon of non-uniform shrinkage and the influence of concrete mix proportion on drying shrinkage, the theory of non-linear moisture diffusion was applied to model shrinkage in the long reinforced concrete structure with the original mix proportion and the optimised one. The three-dimensional numerical simulation was implemented based on the thermal–structural coupled analysis by ANSYS, considering the solution analogy between the moisture field and the temperature field. The moisture field and shrinkage induced stress field in concrete were calculated. The results show that the minimum relative humidity is greater, and the maximum humidity gradient is smaller in the structure with the optimised mix proportion than that in the structure with the original one due to the slower moisture diffusion. Consequently, the optimisation of mix proportion improves the cracking resistance prominently, for the cracking time and crack propagation are delayed significantly.

Correlation Research of Concrete Mix Proportion on Cement Dosage in Coarse Aggregate

Along with the high-speed development of social economy in our country, the country invests more in infrastructure construction. The ratio of concrete in coarse aggregate has great impact on engineering quality. If there are any proportion problems, a certain degree of engineering accidents and sometimes even devastating accidents can be caused. This article studies the correlation between concrete proportioning and cement dosage in coarse aggregate through practices, discovers the importance of reasonable selection of coarse aggregate in economic cement mixing ratio configuration process, and realizes the implementation of project cost reduction in project design.

콘크리트의 레올로지 특성에 따른 펌핑관내 마찰저항계수의 예측에 관한 연구

The establishment of the technology for evaluating friction resistance and pipe pressure and the relation of the fluid characteristics and pumpability of concrete is essential for concrete pumping performance for the rapid construction of super-tall buildings. In this study, a quantitative evaluation of concrete fluid characteristics and surface friction resistance was performed, applying different concrete mix proportions and pumping conditions. To achieve this, we developed a temporary horizontal pumping evaluation system to measure pipe pressure and surface friction characteristics, and performed an experiment to investigate the relations between concrete rheology characteristics and friction resistance in pipe. The experiment found that in terms of the rheology characteristics, plastic viscosity was reduced remarkably after pumping. As well, high regression between the surface friction and pressure gradient was confirmed. This means that it is possible to evaluate the friction resistance between concrete and pipe by means of a pumping system that includes a frictional resistance testing pipe. In addition, high regression between the plastic viscosity of concrete after pumping and friction resistance coefficient was confirmed. Finally, it is considered that pumping pressure can be predicted using the friction resistance coefficient derived in this study, and it has high regression

The Effect of Admixtures on Anti-Permeability of C30 Anchor Anti-Seepage Mass Concrete

Abstract. It was based on bridge anchor structure of three gorges reservoir area, from the perspective of enhancing the anti-permeability performance of mass concrete, taking into account the economic perspective, with the use of large dosage of fly ash and slag powder to replace cement to reduce the water-binder ratio and hydration heat, improve the anti-permeability performance of concrete, according to the characteristics of mass concrete. Through the test, the influence law of admixtures on impermeability of C30 mass concrete were obtained, and at the same time the better mix proportion of C30 anti-seepage mass concrete used in bridge anchor structure was recommended.

AN EXPERIMENTAL STUDY ON DURABILITY AND WATER ABSORPTION PROPERTIES OF PERVIOUS CONCRETE

Pervious concrete is a special high porosity concrete used for flatwork applications that allows water from precipitation and other source to pass through there by Reducing the Runoff from a site and Recharging Ground Water Levels. Durability and Water Absorption are important properties of Pervious Concrete. This paper represents the experimental methodology and experimental results related to durability and water absorption. Cylinders of size 100 mm O and 200 mm height are prepared to investigate both these properties. This investigation should be carried out at the end of 28 days for water absorption and 56 days for durability in which cylinders are immersed in Sodium Chloride (NaCl) Solution after 28 days of casting. Different concrete mix proportion such as 1:6, 1:8 and 1:10 with different size of gravel such as 18.75 mm and 9.375 mm should be used to check both these properties of pervious concrete. Test results indicates that pervious concrete made by 1:6 concrete mix proportion has more durability and less water absorption and pervious concrete made by 1:10 mix proportion has more water absorption and less durability that’s why durability and water absorption are inversely proportional to each other.

Effect of supplementary cementitious materials on reduction of CO2 emissions from concrete

The present study examined the effectiveness of supplementary cementitious materials (SCMs) such as ground granulated blast-furnace slag (GGBS), fly ash (FA), and silica fume (SF), in reducing CO2 emissions from ordinary Portland cement (OPC) concrete. This was done by assembling and analyzing a comprehensive database including 5294 laboratory concrete mixes and 3915 plant mixes. The database covered extensive ranges of compressive strength (8–170 MPa) and substitution levels (3–80% for GGBS, 3–70% for FA, and 3–40% for SF). The system studied for CO2 assessment of concrete based on Korean lifecycle inventory was from cradle to preconstruction, which includes consistent materials, transportation and production phases. The unit binder content and CO2 emissions of concrete in developing the unit strength (1 MPa) were identified using the binder intensity and CO2 intensity, respectively. The value of the CO2 intensity decreased sharply as the substitution level of the SCMs increased up to approximately 15–20%, beyond which the rate of decrease gradually slowed. Overall, the binder and CO2 intensities could be formulated as a function of the individual substitution level of each SCM. The proposed equations hold considerable promise as a guideline for the straightforward determination of (1) the total CO2 emission for a given concrete mix proportion, (2) the unit binder content for a targeted compressive strength, and (3) the type and substitution level of SCMs for a designed strength and targeted CO2 reduction rate.

Water Penetration Resistance of Green Concrete Incorporating with Quarry Wastes

In this study, the workability, the compressive strength and the water penetration depth under pressure for concrete incorporate with quarry waste as fine aggregate were investigated. The mix proportions of concrete were set into two classes of water to cement ratio (w/c = 0.4, 0.6). The first class (C1), the mix proportion is 1.0:0.6:2.0:4.0 (Cement: Water: Fine: Coarse). And the second class (C2), the mix proportion is 1.0:0.4:1.5:3.0 and adding the superplasticizer 1% of cement weight. The natural river sand, which use in concrete, was partially replaced by quarry dust at the rates of 0% (no quarry dust), 50% and 100 % by weight of fine aggregate. The results show that concrete containing quarry wastes as fine aggregate decreased the workability and do not significantly affect the 28-day compressive strength whereas concrete incorporating with quarry dusts reduces the water penetration depth.

Design for durability: The key to improving concrete sustainability

There are many ways to reduce the carbon footprint of concrete including reduction in its portland cement clinker content by methods including: (a) optimization of total aggregate gradations, (b) use of water-reducing admixtures, (c) intergrinding clinker with limestone, and (d) use of supplementary cementing materials (SCMs). However, the most effective way to improve sustainability of concrete structures is by making them last longer through design for durability, and by minimization of construction defects. In almost every case, durable concretes will include all of the above listed aspects, but from a design approach, the emphasis needs to be on durability. Durability design includes more than the selection of concrete materials and mix proportions. It also requires that construction detailing, temperature control, adequate compaction, protection of fresh concrete, and curing be detailed in the specification and that inspection and testing be carried out to ensure that the specifications are being followed. The performance requirements need to be stated explicitly, and the objectives made clear. In addition to discussing various aspects of concrete durability, this contribution will discuss the merits of performance and objective-based specifications as well as the processes required to make them work.

コンクリートの施工がエントレインドエアに及ぼす影響

Generally, air-entraining agent is used for improving the freeze-thaw resistance of concrete. Entrained air exists as independent microscopic bubbles in fresh concrete. Air-voids less than 0.3mm in diameter and its homogeneous distribution are effective for improving the freeze-thaw resistance. However, unsuitable concrete works, for instance exceeded vibration of fresh concrete at compacting work and unsuitable mix proportions can cause the loss of microscopic bubbles and affect the freeze-thaw resistance of hardened concrete. In this study, the effect of segregation of fresh concrete due to unsuitable works and mix proportions on the air-void distribution of hardened concrete was investigated. Various mix proportions of concrete were prepared and the effect of unsuitable concrete works, exceeded impact due to free fall from the height of 4.0m without shooter and exceeded horizontal move using internal concrete vibrator was discussed. As a result, it was confirmed that air-void diameter and air content in hardened concrete was influenced by concrete works and mix proportions. Total amount of microscopic bubbles below 0.3mm in diameter were reduced by unsuitable concrete works and the loss was significant in the mix proportions whose unit weight of water were high. When conventional concrete whose slump was 8cm was used, while the loss of microscopic bubbles due to 4.0m free fall was not significant, the loss of microscopic bubbles by exceeded vibration was remarkable. From these results, it was confirmed that the suitable viscosity of cement mortar is important to eliminate the risk of deterioration by freeze-thawing.一般にコンクリートに凍結融解抵抗性を付与する場合、化学混和剤を用いてフレッシュコンクリートにエントレインドエアを導入している。エントレインドエアはフレッシュコンクリート内部で微細な独立気泡として存在し、硬化後も適切な気泡径と量が保たれていれば、凍結融解抵抗性の向上がもたらされる。しかし、施工方法によってはエントレインドエアが減少し、硬化後に適切な気泡径と量が確保されない可能性もある。本研究では異なる配合のコンクリートを用いて、施工方法がエントレインドエアの減少や硬化後の気泡径および量に及ぼす影響を検討した。その結果、硬化後の気泡径と量は施工方法と配合に影響を受けることを確認した。

Concrete Mix Design for Service Life of RC Structures under Carbonation Using Genetic Algorithm

Steel corrosion in reinforced concrete (RC) structure is such a critical problem to structural safety that many researches have been performed for maintaining required performance during intended service life. This paper is for a numerical technique for obtaining optimum concrete mix proportions through genetic algorithm (GA) for RC structures under carbonation which is considered as a serious deterioration in underground sites and big cities. For this study, mix proportions and CO2diffusion coefficients are analyzed through the previous studies, and then the fitness function of CO2diffusion coefficient is derived through regression analysis. The fitness function from 69 test results includes 5 variables of mix proportions such as w/c (water to cement) ratio, cement content, sand content percentage, coarse aggregate content, and R.H. (relative humidity). Through GA technique, simulated mix proportions are obtained for 12 cases of verification and they show reasonable results with average relative error of 4.6%. Assuming intended service life and design parameters, intended CO2diffusion coefficients and cement contents are determined and then related mix proportions are simulated. The proposed technique can provide initial concrete mix proportions which satisfy service life under carbonation.

Evaluation Technique of Chloride Penetration Using Apparent Diffusion Coefficient and Neural Network Algorithm

Diffusion coefficient from chloride migration test is currently used; however this cannot provide a conventional solution like total chloride contents since it depicts only ion migration velocity in electrical field. This paper proposes a simple analysis technique for chloride behavior using apparent diffusion coefficient from neural network algorithm with time-dependent diffusion phenomena. For this work, thirty mix proportions of high performance concrete are prepared and their diffusion coefficients are obtained after long term-NaCl submerged test. Considering time-dependent diffusion coefficient based on Fick’s 2nd Law and NNA (neural network algorithm), analysis technique for chloride penetration is proposed. The applicability of the proposed technique is verified through the results from accelerated test, long term submerged test, and field investigation results.

Optimal design for the mortar-filled glass fibre-reinforced polymer tube dowels

Use of mortar-filled glass fibre-reinforced polymer (GFRP) tubes is considered as an alternative of steel dowel bars in concrete pavement. The mortar-filled GFRP tubes have two major advantages over conventional steel dowels: its stiffness is comparable to that of concrete and it has a high corrosion resistance. In the present study, five different types of mortar, made with different concrete materials and mix proportions, were used to fill up a given GFRP tube. The mechanical properties, such as flexural and shear strength, of these mortar-filled GFRP tubes were investigated. One mortar-filled GFRP tube was then selected and used as dowels in field pavement. The field performance of the mortar-filled GFRP tube dowels was evaluated. The results indicate that the GFRP tube dowels have sufficient load transfer capacity and the overall performance of the GFRP tube dowels is comparable to that of steel dowel.